a chiller is the best solution. My water has been a few degrees warmer than I would like so I use Hydroguard to curb the unwanted growth in the water. Botanicare makes it. Voodoo juice is similar and from the research I've done, it's even better. It's really expensive though.
it's not as if I'm going to throw all of my equipment away after only one run. It's a perpetual thing, so I'll divide my cost by what I make over the coarse of the full life of the equipment.
For what we use this equipment for, the cost is usually offset. Ya know what I'm sayin'? I have 1 good 4x8 and I have one that I only use for veg because of light leaks and what not. As far as gorilla tents go, when it's time to replace, that's what I will be using. Hopefully I can start...